In-packaged multi-channel light engine on single substrate

ABSTRACT

An in-packaged multi-channel light engine is packaged for four or more sub-assemblies of optical-electrical sub-modules. Each is assembled with at least four laser chips, one or more driver chip, and one or more trans-impedance amplifier (TIA) chip separately flip-mounted on a silicon photonics interposer and is coupled to an optical interface block and an electrical interface block on a sub-module substrate. The in-packaged multi-channel light engine further includes a first frame fixture holding the four or more sub-assemblies and a second frame fixture configured to hold the first frame fixture with the four or more sub-assemblies. The in-packaged multi-channel light engine further includes an interposer plate inserted between the sub-module substrates and a module substrate and is compressed between a backplate member attached to a bottom side of the module substrate and a top plate member configured as a heatsink with a plurality of fin structures.

BACKGROUND OF THE INVENTION

The present invention relates to optical telecommunication techniques. More particularly, the present invention provides an in-packaged optical-electrical module assembling multiple sub-modules each being configured as a multi-channel light engine containing an optical-electrical transceiver based on silicon-photonics platform, and an optical-electrical system having the same.

As science and technology are updated rapidly, processing speed and capacity of the computer increase correspondingly. The communication transmission or reception using the traditional cable is limited to bandwidth and transmission speed of the traditional cable and mass information transmission required in modern life causes the traditional communication transmission overload. To correspond to such requirement, the optical fiber transmission system replaces the traditional communication transmission system gradually. The optical fiber communication is chosen for systems requiring higher bandwidth and longer distance that electrical cable cannot accommodate. Present electronic industrial performs research toward optical transmission which will become the mainstream in the future even for short distance communication. Said optical communication is a technology in that light wave functions as signal carrier and transmitted between two nodes via the optical fiber. An optical communication system includes an optical transmitter and an optical receiver. By the optical transceiver, the received optical signal can be converted to an electrical signal capable of being processed by an IC, or the processed electrical signal can be converted to the optical signal to be transmitted via optical fiber. Therefore, objective of communication can be achieved.

Over the last few decades, the use of communication networks exploded. In the early days Internet, popular applications were limited to emails, bulletin board, and mostly informational and text-based web page surfing, and the amount of data transferred was usually relatively small. Today, Internet and mobile applications demand a huge amount of bandwidth for transferring photo, video, music, and other multimedia files. For example, a social network like Facebook processes more than 500 TB of data daily. With such high demands on data and data transfer, existing data communication systems need to be improved to address these needs.

40-Gbit/s and then 100-Gbit/s data rates wide-band WDM (Wavelength Division Multiplexed) optical transmission over existing single-mode fiber is a target for the next generation of fiber-optic communication networks. More recently, optical components are being integrated on silicon (Si) substrates for fabricating large-scale silicon photonics integrated circuits that co-exist with micro-electronic chips. Chip-scale lasers packaged directly within silicon photonics opto-electrical system have been of interest for many applications such as wide-band DWDM or CWDM communication and wavelength-steered light detection. A whole range of photonic components, including filters, (de)multiplexers, splitters, modulators, and photodetectors, have been demonstrated, mostly in the silicon-on-insulator (SOI) platform. The SOI platform is especially suited for standard DWDM communication bands around 1550 nm or CWDM communication band around 1310 nm, as silicon (n=3.48) and its oxide SiO₂ (n=1.44) are both transparent, and form high-index contrast, high-confinement waveguides ideally suited for medium to high-integration planar integrated circuits (PICs).

With the advances of optical communication technology and applications driven by the market, the demands become stronger on increasing bandwidth for optical communication and decreasing package footprint of an optical transceiver. It is more and more challenging to integrate all necessary components within smaller and smaller module package. For the state-of-art optical transceiver products, all the critical components including clock data recovery (CDRs), modulator drivers, transimpedance amplifiers (TIAs), and PLC photonics blocks having optical passives, modulators, and photo detectors, are assembled side-by-side on a same SOI-based component substrate in a 2D fashion. This approach has at least two drawbacks for developing any future optical transceiver with data rate greater than 400 G. Firstly, the side-by-side placement of the components consumes much of the board area for optical transceiver as a pluggable product or major substrate area for on-board optics product, making it very difficult to further shrink the product size. Secondly, side-by-side placement on the substrate creates longer electrical transmission length and often requires wire bonds between electrical die and photonics die, introducing more electrical loss which damages signal integrity for very high data rate transceiver product, e.g., >56 Gbaud symbol rate. In particular, the wire bonds lead to impedance mismatch due to large inductance, degrading the signal at higher frequencies. As such, it is not practical to use wirebond as electrical interconnect between chips or between chips and board for the applications where high frequency (e.g., >40 GHz) analog signal is transmitted. The large inductance of wire bonds has become a bottle neck of high-speed data transmission.

To shorten the interconnect length of conventional wire bonds between electronics devices (e.g., from modulator driver/TIA to digital signal processor DSP) or between electronics (driver/TIA) and photonics (e.g., CDR and PAM4 ASIC), people have started to use through-silicon via (TSV) process and silicon interposer in Si photonics die to replace wire bonds and make interconnections. With the advancement of silicon TSV manufacturing process for making Si photonics components and integrating active components with wafer-level assembly and burn-in testing, an in-packaged optical-electrical module assembling multiple light engines on a single module substrate would provide great high-performance benefit and desired bandwidth capacity for various applications involving backplane reach, or medium reach, or short reach, or extra-short reach interconnect switch for high-speed data communication.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to optical telecommunication techniques. More particularly, the present invention provides an in-packaged optical-electrical module assembling multiple sub-modules on a single line card, each being configured as a multi-channel light engine containing an optical-electrical transceiver based on silicon-photonics platform. Merely by example, the present invention discloses a sub-assembly for the sub-module integrating multiple laser chips providing multiple CWDM channels on a single silicon photonics substrate, a compact package for multiple such sub-assemblies of sub-modules on a single line card providing 1.6 Tbit/s or higher total data switching capacity in various applications of high-speed data communication with different interconnect lengths, though other applications are possible.

In modern electrical interconnect systems, high-speed serial links have replaced parallel data buses, and serial link speed is rapidly increasing due to the evolution of CMOS technology. Internet bandwidth doubles almost every two years following Moore's Law. But Moore's Law is coming to an end in the next decade. Standard CMOS silicon transistors will stop scaling around 3 nm. And the internet bandwidth increasing due to process scaling will plateau. But Internet and mobile applications continuously demand a huge amount of bandwidth for transferring photo, video, music, and other multimedia files. This disclosure describes techniques and methods to improve the communication bandwidth beyond Moore's law.

In an embodiment, the present invention provides an in-packaged multi-channel light engine. The in-packaged multi-channel light engine includes four or more sub-assemblies of optical-electrical sub-modules. Each sub-assembly is assembled in a case formed with a lid member covering a peripheral side member over peripheral edge region of a sub-module substrate. Each optical-electrical sub-module includes at least four laser chips, one or more driver chips, and one or more trans-impedance amplifier (TIA) chips separately flip-mounted on a silicon photonics substrate and is coupled to an optical interface block and an electrical interface block commonly mounted on the corresponding sub-module substrate. The in-packaged multi-channel light engine further includes a first frame fixture with a crossly-joined bar across middle region to form four or more window structures configured to allow the four or more sub-assemblies to be fitted in respectively with top surfaces of the lid members on top and bottom sides of the corresponding sub-module substrates at bottom. Additionally, the in-packaged multi-channel light engine includes a second frame fixture configured to hold the first frame fixture with the four or more sub-assemblies. The in-packaged multi-channel light engine further includes an interposer plate having a top side with four or more first-sets of conducting bumps, a bottom side with four or more second-sets of patterned conducting bumps, and a plurality of through-plate conducting vias and interior conducting paths configured to connect the first-sets of conducting bumps with the four or more second-sets of patterned conducting bumps. Each first-set of conducting bumps is configured to bond to a respective sub-module substrate. Furthermore, the in-packaged multi-channel light engine includes a module substrate having a top side with four or more sets of conducting bump contacts configured to respectively bond to the four or more second-sets of conducting bumps. The in-packaged multi-channel light engine further includes a backplate member attached to a bottom side of the module substrate. Moreover, the in-packaged multi-channel light engine includes a top plate member configured to compress the second frame fixture that holds the first frame fixture with the four or more sub-assemblies, the interposer plate, and the module substrate vertically together with the backplate member. The top plate member is configured as a heatsink with a plurality of fin structures.

In a specific embodiment, the present invention provides a sub-assembly of a multi-channel light engine. The sub-assembly includes a sub-module substrate severed as a bottom member and a peripheral frame member having four sides disposed along a peripheral region on a front surface of the sub-module substrate. The peripheral frame member has an open slot through at least one side. The sub-assembly further includes a silicon photonics substrate electrically bonded via through-substrate vias bump contacts on the front surface of the sub-module substrate. The silicon photonics substrate is configured to fabricate multiple Si-based waveguide devices therein. Additionally, the sub-assembly includes one or more driver chips, one or more transimpedance amplifier chips, and multiple laser chips separately mounted on the silicon photonics substrate and coupled to corresponding Si-based waveguide devices to form a transmitter unit and a receiver unit. The sub-assembly further includes an optical interface block containing multiple planar waveguides formed on a glass or sapphire substrate mounted on the front surface of the sub-module substrate next to the silicon photonics substrate. The multiple planar waveguides are optically coupled to corresponding Si-based waveguide devices and optical fibers in a fiber cable laid through the open slot through the at least one side. The optical interface block is configured to deliver output transmitted from the transmitter unit to an output optical fiber and to receive incoming multi-wavelength light signal from an input optical fiber for the receiver unit. Furthermore, the sub-assembly includes an electrical interface block including multiple ASIC chips mounted on the front surface of the sub-module substrate or a back surface thereof and configured to receive data signals based on which control signals for the laser chips are generated for producing multi-channel optical signals and process digital signals converted from the incoming light signal for electrical host. Moreover, the sub-assembly includes a top lid member covering the peripheral frame member to enclose the light engine.

The present invention achieves these benefits and others in the context of known waveguide laser modulation technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following diagrams are merely examples, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this process and scope of the appended claims.

FIG. 1 is a simplified block diagram of an integrated optical-electrical sub-module according to an embodiment of the present invention.

FIG. 2 is an exemplary diagram of an optical-electrical transceiver integrating 4 lasers providing 4 CWDM channels plus 4 replicate channels according to an embodiment of the present invention.

FIG. 3 is a schematic top view of wafer level assembly of a plurality of in-packaged silicon photonics chips on a single substrate according to an embodiment of the present invention.

FIG. 4 is a schematic top view of an in-packaged optical-electrical module of four sub-module light engines according to an embodiment of the present invention.

FIG. 5 is an exploded view of a package for the optical-electrical module of FIG. 4 integrated with a heatsink and interfaced to a line card printed circuit board according to an embodiment of the present invention.

FIG. 6 is an exploded view of a sub-assembly of four sub-module light engines in the package of FIG. 5 according to an embodiment of the present invention.

FIG. 7 is an exploded view of a sub-assembly of one sub-module light engine in the sub-assembly of FIG. 6 according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to optical telecommunication techniques. More particularly, the present invention provides an in-packaged optical-electrical module assembling multiple sub-modules on a single line card, each being configured as a multi-channel light engine containing an optical-electrical transceiver based on silicon-photonics platform. Merely by example, the present invention discloses a sub-assembly for the sub-module integrating 4 laser chips providing 4 CWDM channels plus 4 optional replicated CWDM channels on a single silicon photonics substrate, a compact package for multiple such sub-assemblies of sub-modules on a single line card providing 0.4 Tbit/s or higher per sub-module for building desired switching capacity in various applications of high-speed data communication with different interconnect lengths, though other applications are possible.

The following description is presented to enable one of ordinary skill in the art to make and use the invention and to incorporate it in the context of particular applications. Various modifications, as well as a variety of uses in different applications will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to a wide range of embodiments. Thus, the present invention is not intended to be limited to the embodiments presented, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without necessarily being limited to these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All the features disclosed in this specification, (including any accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Furthermore, any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. Section 112, Paragraph 6. In particular, the use of “step of” or “act of” in the Claims herein is not intended to invoke the provisions of 35 U.S.C. 112, Paragraph 6.

Please note, if used, the labels left, right, front, back, top, bottom, forward, reverse, clockwise and counter-clockwise have been used for convenience purposes only and are not intended to imply any particular fixed direction. Instead, they are used to reflect relative locations and/or directions between various portions of an object.

In an aspect, the present disclosure provides an integrated optical-electrical sub-module based on silicon photonics platform and an in-packaged optics assembly of four or more sub-modules on one module substrate with 1.6 Tbit/s or higher optical lane speeds for PAM backplane/optical reach for various interconnect ranges of data communication. As data transmission-capacities increase in WDM systems, demand on high-speed, compact optical transceiver based on silicon photonics platform increasingly attract more and more interest over the recent years. For example, a pluggable optical transceiver in compact form factor. Yet, the compact optical transceiver is still a stand-alone device that needs to be coupled with separate passive optical devices like Mux/Demux and one or more Gearbox or Retimer chips to connect with an electrical switch device to form a functional light engine, which requires a fairly large package size and high power-consumption.

FIG. 1 shows a simplified block diagram of an integrated optical-electrical sub-module according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, in an embodiment, the integrated optical-electrical sub-module includes an electrical host interface configured to receive electrical host data input via N 25 G (NRZ) or 50 G (PAM4) or 100 G (PAM4) channels and a digital processor to process the data signals via Retimer chip having N to N lanes. Optionally, the digital processor processes the data signal via a Gear box N to M lanes where N is a multiple of M. Optionally, the electrical host interface is configured in one or more chips including forward error correction (FEC) channel coding for controlling errors in data transmission over unreliable or noisy communication channels. In the embodiment, the integrated optical-electrical sub-module also includes an optical line interface configured with 4-wavelength CWDM lasers modulated to convert N electrical data into optical signals in N optical lanes. Optionally, a light engine with similar configuration can be formed with >4 wavelengths. Optionally, the 4 or more wavelengths may be chosen to have half spacing than nominal CWDM channels. The optical signals are transmitted via optical line data output multiplexed in a waveguide or optical fiber. Optionally, the laser chips, a Driver chip, and a Transimpedance Amplifier (TIA) chip are integrated on a silicon photonics substrate. Optionally, the silicon photonics substrate is mounted via an interposer on a same sub-module substrate for mounting the one or more chips containing the electrical host interface. Optionally, the silicon photonics substrate is the interposer. Optionally, an analog control chip for laser and modulator control is mounted on a backside of the sub-module substrate. Optionally, TIA chip or Driver chip or microcontroller chip can be mounted on the backside of the sub-module substrate as well. Optionally, the integrated optical-electrical sub-module is configured to have an external power interface to couple with a power supply and receive module control signals via a host control interface such as I2C interface.

FIG. 2 is an exemplary diagram of an optical-electrical transceiver integrating 4 lasers providing 4 CWDM channels plus 4 replicate channels according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. In an embodiment, the optical-electrical transceiver 1000 integrates four laser chips 110 with a driver chip 150 and a TIA chip 140 flip-bonded on a silicon photonics (SiPho) substrate 100 to form a SiPho chip coupled with an external planar light circuit (PLC) block 200. As shown, the optical-electrical transceiver 1000 is specifically configured as a 4-wavelength CWDM optical transceiver including an optical receive path and an optical transmit path. In the optical receive path, it is configured to receive incoming four light signals with four wavelengths demultiplexed from one optical input 221. In the optical transmit path, it is configured to output four light signals with four CWDM channel wavelengths multiplexed to one optical output 211. A 4-to-1 multiplexer (Mux) 210 is a PLC waveguide device formed on a glass or sapphire substrate and configured to multiplex the four CWDM channel wavelengths into one waveguide or optical fiber. A 1-to-4 demultiplexer (Demux) 220 is another PLC waveguide device formed on the same glass or sapphire substrate and configured to demultiplex an incoming optical signal to four multiplexed wavelengths which carry high-speed modulated signals from the network. The optical-electrical transceiver 1000 also includes multiple high-speed photodetectors 130 to detect each of the four light signals with four demultiplexed wavelengths. In the embodiment, both the Mux 210 and Demux 220 are integrated in the PLC block 200. Optionally, the PLC block 200 includes multiple optical waveguides formed in a single glass or sapphire substrate aligned with corresponding waveguides in the silicon photonics substrate 100.

Referring to FIG. 2, the optical-electrical transceiver 1000 includes a bank of 4 CWDM lasers 110 respectively provide 4 light signals with respective CWDM channel wavelengths centered in 1270 nm, 1290 nm, 1310 nm, and 1330 nm. Optionally, each laser device is a DFB laser chip. Optionally, each laser chip 110 is provided as an individual laser chip fabricated separately and flip-mounted on the silicon photonics substrate 100. Optionally, each light signal outputted from the respective one laser chip is aligned to a silicon waveguide built in the silicon photonics substrate 100. Each light signal, through the silicon waveguide, is firstly coupled into a power splitter 120 and is split into two light signals in two separate branches with a split ratio varying from 5:95 to 50:50. Optionally, one split light signal from a minor split branch of the power splitter 120 is used for monitoring or wavelength locking or feedback control. Optionally, one light signal from one major split branch of the power splitter 120 is fed to one of four modulators 160. Optionally, the power splitter is a 50:50 splitter, the light signal is converted to two replicate light signals, basically doubling the channel numbers. Each replicate light signal is fed into a modulator. Totally, the optical-electrical transceiver 1000 of FIG. 2 shows four modulators 160 respectively for receiving light signals from four first branches (01) while four other modulators for the four second (replicate) branches (02) are not explicitly shown. Of course, there can be many variations in functional setups or optical layouts to handle these light signals and configure in different manners for different applications of the optical-electrical sub-module other than the one optical-electrical transceiver including 4 CWDM channels plus 4 replicate CWDM channels. For example, optionally, the optical-electrical transceiver 1000 is provided with a set (>4) of lasers with a smaller channel spacing than the CWDM channels to provide >4 wavelengths. The whole system will then have to operate in the same multi-wavelength plan.

Optionally, the modulator 160 in any one of first branch 01 is configured in a linear waveguide-based Mach-Zehnder modulation scheme. Each modulator 160 includes two waveguide branches with desired phase delay configured to match with respective one of four wavelengths 1270 nm, 1290 nm, 1310 nm, and 1330 nm of the four CWDM channels. Optionally, the four wavelengths can be selected from a group of 1270 nm, 1280 nm, 1290 nm, and 1300 nm or a group of 1300 nm, 1310 nm, 1320 nm, and 1330 nm with smaller channel spacing. A Driver module 150 is provided as a separately fabricated CMOS or SiGe chip flip-mounted on the same silicon photonics substrate 100. Optionally, a redundant or a replicate driver module 150′ (not shown in FIG. 2) is also provided as a chip flip-mounted on the same silicon photonics substrate 100 for driving the other four modulators in the replicate split branch (not shown). The driver module 150 is configured to drive all the four modulators 160 to modulate the light signals in the four CWDM channels. Optionally, one 8-channel driver is able to drive the 4 channels plus 4 replicate channels. Optionally, the driver module 150 employs PAM-N(N is an integer) modulation protocol or NRZ modulation protocol to modulate the light signal. For example, the modulators 160 are provided as silicon-waveguide-based Mach-Zehnder interferometer configured to provide PAM4 modulation though other formats can be employed. After modulation, the four CWDM channels of light signals are guided to the 4-to-1 multiplexer (Mux) 210 in the PLC block 200 which outputs a multiplexed light signal through an optical fiber (not shown) to an output port 211 of the sub-module 1000. Optionally, there is another 4-to-1 Mux (yet not shown) formed in the PLC block 200 for combining the other 4 replicate CWDM channels of light signals to one multiplexed light signal which is through another fiber (not shown) led to the output port 211. Effectively, a combination of the 4 laser chips 110 and 4 or 8 modulators 160 driven by the driver module 150 or plus a replicate driver module 150′ forms an integrated 4-ch optical transmit path plus another 4-ch replicate optical transmit path (not shown in FIG. 2).

Referring to FIG. 2 again, the optical-electrical transceiver sub-module 1000 includes a 4-ch optical receive path. In the optical receive path, the optical de-multiplexer (Demux) 220 in the PLC block 200 receives an incoming light signal via an input port 221 from an external network which is configured to operate under the four CWDM channel wavelengths for transmitting corresponding data signals. The incoming light signal carrying four multiplexed wavelengths is demultiplexed into 4 separate light signals in the respective 4 wavelengths guided into respective four waveguides formed in the silicon photonics substrate 100. The High-speed photodetectors 130 are used to detect these four light signals separately and converted to respective electrical current signals. In the embodiment, the 4-channel optical receive path of the optical-electrical transceiver sub-module 1000 also includes a trans-impedance amplifier (TIA) module 140 for independently processing the electrical current signals converted from respective four separate light signals for communicating with host electrical network system via an electrical host interface. Optionally, the TIA module 140 is separately formed and flip-mounted on the same silicon photonics substrate 100. Optionally, the optical-electrical transceiver sub-module 1000 also includes a replicate 4-ch optical receive path as the four replicate channel light signals can be demultiplexed from another incoming light by another demultiplexer. In the replicate 4-ch optical receive path, a replicate TIA module 140′ (not shown) can be included for independently processing four more electrical signals converted from respective four replicate light signals for communicating with host electrical network system with 2× expanded bandwidth. Optionally, the TIA module 140′ is also a flip chip mounted on the same silicon photonics substrate.

In another aspect, the present disclosure provides a fabrication process for the integrated optical-electrical sub-module based on silicon photonics platform such as the transceiver sub-module 1000. In some embodiments, the fabrication process includes wafer level assembly of 2.5D silicon photonics substrate involving 2.5D silicon interposer and 220 nm silicon-on-insulator (SOI) substrate. The process includes monolithic formation of multiple silicon or silicon nitride waveguides in the silicon photonics substrate 100 for connecting or aligning with several different silicon photonics devices including power splitters, SiGe or Ge high-speed photodetectors, and Si/SiN-based Mach-Zehnder interferometer modulator devices formed in the same silicon photonics substrate 100. The process also includes coupling the silicon waveguides with passive PLC devices such as optical multiplexers and demultiplexers formed on a glass or sapphire substrate and mounted onto the silicon photonics substrate as PLC block 200. The process further includes flip-mounting active devices such as laser chips to the silicon photonics substrate as an in-packaged design and align the laser chips directly to the waveguides in the silicon photonics substrate or PLC devices in the PLC block. Optionally, some of the silicon photonics components mentioned above are also silicon waveguides themselves monolithically formed in a same manufacture process for preparing the silicon photonics substrate to integrate the optical-electrical transceiver sub-module 1000.

FIG. 3 shows a schematic top view of a wafer level assembly of a plurality of in-packaged silicon photonics chips on a single substrate according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As shown, using the integrated optical-electrical transceiver sub-module as an example, the silicon photonics substrate 100 is one die fabricated from a CMOS compatible process plus a post CMOS wafer level assembly out of a SOI wafer 10. In an example, each die 100 is used to form an optical-electrical module by directly processing the SOI wafer to form a silicon photonics through-substrate via (TSV) interposer. More details of the fabrication process involving the TSV interposer can be found in U.S. patent application Ser. No. 15/887,758 filed Feb. 2, 2018 and commonly assigned to Inphi Corp. Santa Clara, Calif. The as-mentioned application is incorporated by reference herein for all purposes. Utilizing the silicon photonics TSV interposer several optical or electrical components for forming the optical-electrical module can be directly mounted on. Referring to FIG. 3, the one die 100 in the wafer 10 is enlarged out, showing that several electrical and optical components including two driver chips 150, 150′, two TIA chips 140, 140′, two dummy chips 190, and four field effect transistors 145 (to apply bias to the laser chips 110) is flip-mounted on the top side of the die in a post CMOS wafer level assembly. Especially, four laser chips 110 are also directly flip-mounted to respective chip sites on the die and optically aligned with waveguides formed therein as an in-packaged assembly without any extra wire bonding.

Additionally referring to FIG. 3, multiple redundant dies are arranged in multiple pairs of rows on the wafer substrate 10. Each die 100 includes four CWDM laser chips 110. The wafer substrate 10 also is configured to lay out multiple rows of blink probing pads 300 designed for conducting wafer level burn-in and testing conveniently. Each probing pad 300 includes electrodes 310 for easily coupling with external tester electrodes to allow proper bias current being applied in series to a plurality of laser chips on the wafer substrate 10. More details on designing a chip site on the die for mounting a laser chip and performing wafer level burn-in and testing for the laser chip can be found in U.S. patent application Ser. No. 16/800,974, filed Feb. 25, 2020, which is commonly assigned to Inphi Corp. Santa Clara, Calif. and incorporated by reference herein for all purposes.

In yet another aspect, the present disclosure provides an in-packaged optical-electrical module assembling four optical-electrical sub-modules as mentioned above. FIG. 4 shows a schematic top view of an in-packaged optical-electrical module of four sub-module light engines according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. In an embodiment shown in FIG. 4, the in-packaged optical-electrical module 3000 is provided by integrating four sub-modules 2000A, 2000B, 2000C, and 2000D evenly packaged in four compact areas on a common component substrate 2001. Optionally, each sub-module is formed on its own component substrate which is named as a sub-module substrate.

Each of the four sub-modules in FIG. 4 is substantially redundant and independently functioned as a 4-wavelength transceiver driven by 4 in-packaged lasers to provide 4 light signals for 4 CWDM channels plus 4 replicate CWDM channels as shown in a block diagram of FIG. 2. Optionally, the in-packaged optical-electrical module can integrate two sub-modules. Optionally, the in-packaged optical-electrical module can integrate 6 sub-modules or more. Referring to FIG. 4, in an example, each 4-wavelength transceiver includes a silicon-photonics (SiPho) chip 100 diced from one die from the wafer substrate 10 of FIG. 3. The four CWDM channels are provided by four light signals at respective four CWDM channel wavelengths centered at, 1270 nm, 1290 nm, 1310 nm, and 1330 nm from respective 4 laser chips 110 that are directly flip-mounted on the SiPho chip 100 with its p-side facing toward the SiPho chip. The laser light emitted from each laser chip 110 is aligned to a Si-based waveguide formed in the SiPho chip 100. Optionally, the Si-based waveguide includes an optical splitter to split the laser light to two branches to provide 4 CWDM channels and 4 replicate CWDM channels.

Correspondingly, on each SiPho Chip 100, one driver chip 150 and one TIA chip 140 are included for handling transmission and detection of light signals involving the 4 CWDM channels and one replicate driver chip 150′ and one replicate TIA chip 140′ are included for handling transmission and detection of light signals associated with the 4 replicate CWDM channels. The SiPho chip 100 is coupled to a planar light circuit (PLC) block 200, both being bonded to a top side of the corresponding sub-module substrate 2001.

Optionally, each of the four sub-modules in FIG. 4, e.g., 2000A in upper left portion, also includes a digital signal processing (DSP) chip 2030 plus an replicate one DSP chip 2030′ and a microcontroller chip 2040, all mounted on the same top side of the sub-module substrate 2001 as the SiPho chip 100 and PLC block 200. Both the driver chip 150 and the driver chip 150′ are interfaced via an electrical host interface with external electrical host system respectively through the digital signal processing (DSP) chips 2030 (and 2030′) to handle the electrical data input from an electrical host. The DSP chips also are configured to interact via a host control interface with the microcontroller chip 2040 to provide module control and power supply required for operating the SiPho chip 100. Optionally, the DSP chips 2030 and 2030′ include a Gearbox or Retimer chip for converting analog signals to digital signals through N to N lanes electrical data transfer, a digital processor for processing the digital signals, one or more interface devices for communicating with external electrical host, and current drivers for driving the four laser chips. Optionally, the microcontroller chip 2040 is associated with a respective one sub-module 2000A and is configured to control operations of the DSP chips 2030, drivers 150, TIA 140, and interfaces therein. Optionally, the modulators in the SiPho chip 100 are configured to modulate the laser light signals based on PAM-N protocol, for example, PAM-4 protocol, or based on NRZ protocol. Optionally, the modulators are configured in a Mach-Zehnder Interferometer formed with Si-based waveguides in the silicon photonics substrate.

The PLC block 200 associated with each of the four sub-modules 2000A (through 2000D) includes at least a first optical multiplexer (see FIG. 2) in an optical transmit path to multiplex the four light signals of the four CWDM channels into one output light in one optical fiber and a second optical multiplexer in a replicate optical transmit path to multiplex the four replicated light signals into another output light in another optical fiber. Each optical multiplexer in the PLC block 200 is a planar waveguide formed on a glass or sapphire substrate and properly coupled to one optical fiber. Both optical fibers can be packaged into one on-board fiber cable 2010A (through 2010D) coupled between the PLC block 200. For each sub-module, e.g., 2000A, one optical transceiver transmits eight total output light signals carrying 4 CWDM channels plus 4 replicate CWDM channels to external optical network. In the embodiment, the compact in-packaged optical-electrical module 3000 totally includes four sub-modules 2000A through 2000D, delivering total 32 CWDM channel signals to the external optical network.

In the embodiment, the PLC block 200 associated with the same one of the four sub-modules, e.g., 2000A (through 2000D), also includes a built-in optical receive path configured to receive incoming light signals via optical fibers from network. The PLC block 200 includes at least a first optical demultiplexer to demultiplex an incoming light signal from one fiber (carrying 4 wavelengths) to four individual light signals with the respective four CWDM channel wavelengths. Each optical demultiplexer in the PLC block 200 is a planar waveguide formed on a glass or sapphire substrate properly coupled to one optical fiber. Each of the four individual light signals is coupled from planar waveguide in the PLC block 200 to the waveguides in the silicon photonics substrate and delivered to a photodetector block (referred to FIG. 2). The photodetector block (130 as shown in FIG. 2) individually detects and converts each light signal to an electrical current signal passed to and processed by a trans-impedance amplifier (TIA) module 140 to generate a voltage signal. The voltage signal is further handled or digitized and processed by on-board DSP chip 2030 and fed to an external electrical host receiver. The incoming light signal as mentioned above can be received via an optical fiber that also is packaged into the on-board fiber cable 2010A. Optionally, a second optical demultiplexer is included in the PLC block 200 for receiving and demultiplexing another incoming light signal carrying 4 replicate CWDM channel wavelengths into a replicate receive optical path to provide additional bandwidth with 4 replicate CWDM channels which can be separately detected by photodetectors and converted to corresponding electrical signals. The electrical signals can be processed by a replicated TIA module 140′ and digitally processed by DSP chip 2030′ in the same sub-module.

In this embodiment, PLC block 200 contains two 4-to-1 multiplexer and two 1-to-4 demultiplexer to create two sets of four light paths. For the multi-channel light engine 3000 that packages total four optical-electrical sub-modules 2000A, 2000B, 2000C, 2000D, it can detect different input light signals in 32 channels. In a case that each channel carries data in a rate of 50 Gbit/s, each quadrant sub-module delivers 400 Gbit/s in data rate with 4 CWDM lasers. The in-packaged optical-electrical module 3000 can provide 1.6 Tbit/s data switching communication capacity. In another case with improved modulators, driver chip, TIA chip, and DSP chip, each channel can carry 100 Gbit/s speed even though each quadrant sub-module uses the same 4 CWDM lasers. As a result, the in-packaged optical-electrical module 3000 can expand its data switching communication speed up to 3.2 Tbit/s.

In still another aspect, the present disclosure provides a packaging assembly of the in-packaged optical-electrical module of FIG. 4 as mentioned above. The packaging assembly are illustrated with several exploded views in FIGS. 5, 6, and 7 in different levels of revelation of the packaging structures and mounting fixtures for sub-modules and components therein. FIG. 5 is an exploded view of a packaging assembly 5000 of the in-packaged optical-electrical module of FIG. 4 integrated with a heatsink and interfaced to a module line card based on a printed circuit board according to an embodiment of the present invention. FIG. 6 shows a sub-assembly 3000A for packing four sub-modules within the packaging assembly of the four sub-modules in FIG. 5 according to an embodiment of the present invention. FIG. 7 shows a detailed sub-assembly 2000A of all components in one sub-module in FIG. 5 and FIG. 6 according to an embodiment of the present invention. These diagrams are merely examples, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications.

As shown in FIG. 5, the packaging assembly 5000 is provided by compressing a sub-assembly 3000A of the multi-channel light engine 3000 of FIG. 4 between a top plate member 3020 on top and a backplate member 3060 at bottom. The sub-assembly 3000A of the in-packaged optical-electrical module 3000, as shown in FIG. 6, includes a single piece of solid frame fixture member 3002 having two crossly-linked middle bars to form four closely packed window structures, 3008A, 3008B, 3008C, and 3008D. The four window structures are designed to allow respective four sub-assemblies, i.e., 2000A, 2000B, 2000C, and 2000D to fit in. Each sub-assembly (e.g., 2000A) is designed to have the corresponding sub-module packaged within a case enclosed by a lid member 2200A on top sealed with a peripheral side member 2100A around a peripheral region of a sub-module substrate 2300A at bottom. FIG. 7 shows package structures and component layouts within each sub-assembly of a sub-module (e.g., 2000A). More details will be described in following paragraphs.

Referring to FIG. 6, the solid fixture member 3002 includes notches 3005-1 and 3005-2 at least partially opened downward at one middle bar and one side of the frame fixture member 3002. The lid member (e.g., 2200B) of each sub-assembly (e.g., 2000B) includes an open slot 2105-B facing upward through a length of one side of the peripheral side member 2100B to align with the notch 3005-1. The open slot 2105-B provides an open space for laying a pair of fiber cables 2010AB which respectively packages optical fibers out of the optical-electrical sub-module in the sub-assembly 2000A and 2000B. Similarly, another pair of fiber cables 2010CD also packages optical fibers out of the sub-assembly 2000D and sub-assembly 2000C and is laid in the open space provided by the open slot 2105-C aligned with the notch 3005-2.

Referring to FIG. 5 and FIG. 6, as the sub-assembly 3000A is assembled in the packaging assembly 5000, top surfaces of the lid members (e.g., 2200A) of four sub-assemblies (e.g., 2000A) are mechanically pressed in a good thermal contact against a bottom surface of the top plate member 3020 in the packaging assembly 5000. In an embodiment, as shown in FIG. 5, a top side of the top plate member 3020 is configured with a heatsink having a plurality of fin structures 3021 extended vertically. The height of the plurality of fin structures are designed to help release module heat with a sufficiently high efficiency. Optionally, a thermal pad (not shown) can be inserted between the top surface of the lid members and the bottom surface of the top plate member 3020 to enhance the thermal conductivity. The heatsink is configured to release the heat generated by the four sub-modules in the sub-assembly 3000A in which each sub-module contains 4 CWDM lasers and multiple pre-packaged CMOS chips like the driver chip 150 and TIA chip 140 and DSP chip 2030. Mechanically, the top plate member 3020 is pressed by several spring-loaded compression pins 3030 with threaded head applied from the top side to lock in respective sockets 3063 with the backplate member 3060 in the package assembly 5000.

Referring to FIG. 7, the sub-assembly of the sub-module 2000A includes a case having a top lid member 2200A covering a peripheral side member 2100A located around a peripheral boundary region on top of a sub-module substrate 2300A which is served as a bottom member for the sub-assembly 2000A. Optionally, the sub-assembly 2000A is a quadrant portion fitted in one of four window structures (e.g., 3008A) of the package sub-assembly 3000A. Optionally, the peripheral side member 2100A includes at least an open slot 2105-A for laying at least a fiber cable 2010A for optical input/output fibers of the optical-electrical sub-module in the sub-assembly. Optionally, a top surface 2201A of the lid member 2200A may be attached with a thermal pad (not shown) for enhancing heat release efficiency of the sub-assembly 2000A. Optionally, the sub-module substrate 2300A also is structured to allow heat being conducted effectively through itself.

In one embodiment, as illustrated in FIG. 7, the sub-module packaged in the sub-assembly 2000A includes a SiPho chip packaged on a silicon-photonics substrate 100 which is mounted on a top side of the sub-module substrate 2001A. The SiPho chip 100 is substantially the same as one die formed on a SOI wafer 10 using wafer level assembly process as shown in FIG. 3. Referring to FIG. 7, the SiPho chip 100 includes a driver chip 150 and a replicate driver chip 150′, a TIA chip 140 and a replicate TIA chip 140′, and four laser chips 110, all flip-mounted on top of the same silicon-photonics substrate 100. Some dummy chips (not shown) and field-effect transistor devices 145 can also mounted on top of the same silicon-photonics substrate 100. The SiPho chip includes a transmitter unit configured to generate multi-channel optical signals from the four laser chips which are modulated by four modulator devices driven by the driver chip based on data received via an electrical interface block. The multi-channel optical signals are transmitted to an optical transmit path coupled to an optical interface block to output a multiplexed optical signal.

In the embodiment, the same SiPho chip also includes a receiver unit configured to use a set of photodetectors to detect multi-channel optical signals received in an optical receive path and demultiplexed in the optical interface block from an incoming multiplexed optical signal and use the TIA chip to convert the detected multi-channel optical signals to current signals which are digitized and processed in the electrical interface block before being delivered as N to N lanes of digitized signals for electrical host. including an optical transmit path and an optical receive path in the same silicon photonics substrate 100. One driver chip 150 and one TIA chip 140 in the SiPho chip are involved in handling transmission of four light signals from the four laser chips to the optical transmit path and detecting four incoming light signals from the optical receive path. Another driver chip 150′ and another TIA chip 140′ are separately involved in handling transmission of four replicate light signals from the four laser chips to the optical transmit path and detecting four additional incoming light signals from the optical receive path. These TIA/Driver chips in each SiPho chip of the packaged sub-assembly 2000A are configured to handle reception and transmission of light signals in two replicate sets of 4 CWDM channels with respective wavelengths centered at 1270 nm, 1290 nm, 1310 nm, and 1330 nm. Optionally, the electrical interface block comprises a digital signal processing (DSP) chip 2030 configured to process N to N Lanes of digitized signals with a data rate of 25 Gbit/s per lane. Optionally, the electrical interface block comprises a digital signal processing (DSP) chip 2030 configured to process N to N Lanes of digitized signals with a data rate of 50 Gbit/s per lane. Optionally, the electrical interface block comprises a digital signal processing (DSP) chip 2030 configured to process N to N Lanes of digitized signals with a data rate of 50 Gbit/s per lane. Optionally, the electrical interface block comprises a replicate digital signal processing (DSP) chip 2030′ and a microcontroller chip 2040.

Additionally referring to FIG. 7, disposed along one side of the SiPho chip on the silicon photonics substrate 100, a PLC block 200 is also mounted on the sub-module substrate 2300A. The PLC block 200 includes one or more multiplexers and demultiplexers in PLC-based waveguide formed on a glass or sapphire substrate for guiding light waves to an optical output port and from an optical input port of the sub-assembly 2000A by coupling light signals between the PLC block 200 and input/output optical fibers. The input/output optical fibers per one sub-assembly are packaged in one fiber cable 2005-1.

Furthermore referring to FIG. 7, disposed along another side of the SiPho chip on the silicon photonics substrate 100, one or more ASIC chips, for example, digital signal processing (DSP) chip(s) 2030(2030′), can be flip-mounted on the same sub-module substrate 2300A. Each DSP chip 2030 or 2030′ is configured in an electrical interface block to support functions of one TIA chip 140 and one driver chip 150 for processing or modulating optical/electrical signals involving a 4-ch CWDM optical transmit/receive path or one replicate TIA chip 140′ and one replicate driver chip 150′ for processing or modulating optical/electrical signals involving a replicate 4-ch CWDM transmit/receive path. Moreover, a microcontroller chip 2040 is also flip-mounted to the sub-module substrate 2300A next to the replicate DSP chip 2030′ and configured in the electrical interface block to support operation of the DSP chip or replicate DSP chip as well as the operation of SiPho chip. Referring to FIG. 7, the DSP chips 2030 (2030′), or microcontroller chip 2040 are mounted onto a front side of the sub-module substrate 2300A via multiple conductive bonding bumps 2108. Optionally, the sub-module substrate 2300A also provides its bottom side for mounting additional functional chips for utilizing the substrate more efficiently to enhance performance of the light engine. For example, an ASIC chip 2050 for analog controls for the laser and modulator is mounted at the bottom side of the sub-module substrate 2300A via multiple bumps 2109 based on through-substrate vias.

Referring to FIG. 5 and FIG. 6, the sub-assembly 3000A of the in-packaged light engine 3000 is received by or disposed in a socket frame member 3010 from its top side. An interposer plate 3040 is configured to be disposed between bottom side of the four sub-module substrates (e.g., 2300A) of the sub-assembly 3000A and a top side of a module substrate 3050. Optionally, the four sub-module substrates 2300A through 2300D (see FIG. 6) may be considered as one common substrate. Optionally, the module substrate 3050 is configured to serve as a line card including relevant electrical connection circuits in a printed circuit board (PCB) to the host. Optionally, the module substrate 3050 is a part of a larger line card by itself. The PCB associated with the module substrate 3050 is configured with integrated circuits with a line interface connecting via the four sets of conducting bump contacts to the four sub-assemblies of the optical-electrical sub-modules and configured as a line card with a host interface for connecting the multi-channel light engine to a data center and with an external power interface for accessing external power supply. Optionally, the interposer plate 3040 includes four groups of patterned through-substrate-vias (TSVs) (e.g., 3044A) designed for coupling the bottom sides of four sub-module substrates 2300A through 2300D respectively for the four optical-electrical sub-modules 2000A through 2000D.

Optionally, the interposer plate 3040 is a passive interposer provided with four quadrant grids of conductor-filled through-substrate via (TSVs) bumps respectively formed on four quadrant regions of the interposer plate projected to the four sub-module substrates. For example, the quadrant grid of TSV bumps 3044A is designed for forming electrical connections between the sub-module substrate 2300A to direct bonding interconnects (DBI) contacts 3052A in a corresponding quadrant region of the module substrate 3050. Optionally, each quadrant grid of TSV bumps (e.g., 3044A) is provided to surround a quadrant hollow region (e.g., 3042A) of the interposer plate 3040 to yield the space for optional ASIC chip (e.g., 2050 in FIG. 7) mounted on the back side of the sub-module substrate (e.g., 2300A).

Optionally, the interposer plate 3040 is an active interposer that contains four quadrant grids of TSV bumps to connect IOs and supply as well as to provide active regions with embedded circuit devices to pass electrical signals using buffers between two DBI contacts. Optionally, the interposer plate 3040 is a 2.5D silicon interposer. Optionally, the interposer plate 3040 is a 3D silicon interposer.

Referring to FIG. 5, the module substrate 3050 includes several alignment through-holes 3051 aligned with similar alignment through-holes 3041 in the interposer plate 3040 and that 3011 in the socket frame member 3010. The backplate member 3060 includes an alignment pin 3061 configured to pass through those alignment through-holes 3051, 3041, and 3011 for properly stacking these assembly members together. The module substrate 3050 also has several through-holes 3053 allowing the compression pins 3030 to pass for locking all parts in the package assembly 5000 with the backplate member 3060. The backplate member 3060 includes several opened window regions (e.g, 3062A) designed to provide space for mounting additional chips on the backside of the module substrate 3050. Optionally, these window regions provide better thermal conductivity for the package assembly 5000. The backplate member 3060 has several threaded holes 3063 allowing the corresponding compression pins 3030 with threaded head to lock in there so that the package assembly 5000 is tightly assembled.

While the above is a full description of the specific embodiments, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present invention which is defined by the appended claims. 

What is claimed is:
 1. An in-packaged optical-electrical module comprising: four or more sub-assemblies of optical-electrical sub-modules each being assembled in a case formed with a lid member covering a peripheral side member over peripheral edge region of a sub-module substrate, each optical-electrical sub-module including at least four laser chips, one or more driver chips, and one or more trans-impedance amplifier (TIA) chips separately flip-mounted on a silicon photonics interposer and being coupled to an optical interface block and an electrical interface block commonly mounted on the corresponding sub-module substrate; a first frame fixture with a crossly-joined bar across middle region to form four or more window structures configured to allow the four or more sub-assemblies to be fitted in respectively with top surfaces of the lid members on top and bottom sides of the corresponding sub-module substrates at bottom; a second frame fixture configured to hold the first frame fixture with the four or more sub-assemblies; an interposer plate having a top side with four or more first-sets of conducting bumps, a bottom side with four second-sets of patterned conducting bumps, and a plurality of through-plate conducting vias and interior conducting paths configured to connect the first-sets of conducting bumps with the four or more second-sets of patterned conducting bumps; each first-set of conducting bumps being configured to bond to a respective sub-module substrate; a module substrate having a top side with four or more sets of conducting bump contacts configured to respectively bond to the four or more second-sets of conducting bumps; a backplate member attached to a bottom side of the module substrate; and a top plate member configured to compress the second frame fixture that holds the first frame fixture with the four or more sub-assemblies, the interposer plate, and the module substrate vertically together with the backplate member, the top plate member being configured with a plurality of fin structures to form a heatsink.
 2. The in-packaged optical-electrical module of claim 1 wherein each of the optical-electrical sub-modules comprises: a transmitter unit including the at least four laser chips and four modulator devices driven by the one or more driver chips based on data received via the electrical interface block to generate multi-channel optical signals transmitted to an optical transmit path coupled to the optical interface block to output a multiplexed optical signal; a receiver unit comprising a set of photodetectors configured to detect multi-channel optical signals received in an optical receive path and demultiplexed in the optical interface block from an incoming multiplexed optical signal and the one or more TIA chips configured to convert the detected multi-channel optical signals to current signals which are digitized and processed in the electrical interface block before being delivered as N to N lanes of digitized signals for electrical host.
 3. The in-packaged optical-electrical module of claim 2 wherein the at least four laser chips comprise four DFB laser diode chips flip-mounted with their p-type sides facing toward the silicon photonics interposer and configured to provide four laser lights respectively at four CWDM channel wavelengths centered at 1270 nm, 1290 nm, 1310 nm, and 1330 nm.
 4. The in-packaged optical-electrical module of claim 2 wherein the at least four laser chips provide four laser lights respectively and wherein the transmitter unit comprises a set of four power splitter devices configured respectively to split each of the four laser lights to two portions, one into the optical transmit path and another one into a replicate optical transmit path, both coupling optical signals in respective waveguides coupled to the optical interface block for outputting two multiplexed optical signal to two optical fibers respectively.
 5. The in-packaged optical-electrical module of claim 4 wherein the optical interface block comprises a planar light circuit (PLC) block comprising one or more multiplexing planar waveguide devices and one or more demultiplexing planar waveguide devices formed on a glass or sapphire substrate disposed on the sub-module substrate.
 6. The in-packaged optical-electrical module of claim 5 wherein the PLC block is mounted next to the silicon photonics interposer to allow the one or more multiplexing planar waveguide devices to respectively align with corresponding waveguides associated with the optical transmit path and the replicate optical transmit path in the silicon photonics interposer and couple with respective one output optical fiber associated with each optical transmit path, and to allow the one or more demultiplexing planar waveguide devices to align with corresponding waveguides associated with the optical receive path in the silicon photonics interposer and couple with respective one input optical fiber.
 7. The in-packaged optical-electrical module of claim 6 wherein the receiver unit further comprises a replicate TIA chip and a replicate set of photodetector block configured to detect optical signals from a replicate optical receive path, the replicate optical receive path comprising waveguides in the silicon photonics interposer aligned respectively with the one or more demultiplexing planar waveguide in the PLC block which are coupled with another input optical fiber.
 8. The in-packaged optical-electrical module of claim 7 wherein the optical interface block comprises a fiber cable configured to package two input optical fibers in respective two optical transmit paths and two output optical fibers in respective two optical receive paths.
 9. The in-packaged optical-electrical module of claim 2 wherein each of the four modulator devices comprises a Mach-Zehnder interferometer based on two branches of silicon-based waveguides.
 10. The in-packaged optical-electrical module of claim 9 wherein the at least four laser chips provide four laser lights respectively and wherein the Mach-Zehnder interferometer is configured to modulate a respective one of the four laser lights in PAM-N or NRZ modulation protocol.
 11. The in-packaged optical-electrical module of claim 2 wherein each of the optical-electrical sub-modules further comprises an ASIC chip mounted on a back side of the sub-module substrate and is configured to generate analog driving signals for the one or more driver chips to control the at least four laser chips and the four modulator devices.
 12. The in-packaged optical-electrical module of claim 1 wherein the electrical interface block comprises a digital signal processing (DSP) chip configured with a retimer to process N to N Lanes of digitized signals or a gear box to process N to M lanes with N being a multiple of M, with a data rate of 25 Gbit/s per lane.
 13. The in-packaged optical-electrical module of claim 1 wherein the electrical interface block comprises a digital signal processing (DSP) chip configured with a retimer to process N to N Lanes of digitized signals or a gear box to process N to M lanes with N being a multiple of M, with a data rate of 50 Gbit/s per lane.
 14. The in-packaged optical-electrical module of claim 1 wherein the electrical interface block comprises a digital signal processing (DSP) chip configured with a retimer to process N to N Lanes of digitized signals or a gear box to process N to M lanes with N being a multiple of M, with a data rate of 100 Gbit/s per lane.
 15. The in-packaged optical-electrical module of claim 1 wherein the electrical interface block comprises a replicate digital signal processing (DSP) chip and a microcontroller chip.
 16. The in-packaged optical-electrical module of claim 1 wherein the first frame fixture comprises a notch located on one side of each window structure open up to the top surfaces of the lid member of the one of the four or more sub-assemblies, the lid member and the peripheral side member correspondingly comprises a slot opening aligned with the notch to allow room for a fiber cable connected to the optical interface block.
 17. The in-packaged optical-electrical module of claim 1 wherein the sub-module substrate comprises a plurality of through-silicon-vias filled with conducting material to allow the at least four laser chips, the one or more driver chips, the one or more TIA chips on the silicon photonics interposer as well as other chips mounted on top side of the sub-module substrate to connect to the corresponding first-set of conducting bumps on the interposer plate.
 18. The in-packaged optical-electrical module of claim 1 wherein the interposer plate comprises four or more window openings allowing room for any ASIC chips mounted on bottom side of respective ones of the four or more sub-module substrates.
 19. The in-packaged optical-electrical module of claim 1 wherein the backplate member comprises at least two alignment rods disposed to pass through respective holes in the module substrate, the interposer plate, and the second frame fixture.
 20. The in-packaged optical-electrical module of claim 1 wherein the module substrate comprises a printed circuit board configured with integrated circuits with line interface connecting via the four or more sets of conducting bump contacts to the four or more sub-assemblies of the optical-electrical sub-modules and configured as a line card with a host interface for connecting a multi-channel light engine comprising the four or more sub-assemblies to a data center and with an external power interface for accessing external power supply.
 21. The in-packaged optical-electrical module of claim 1 wherein the top plate member is compressed with the backplate member by at least four spring-loaded pins with threaded lock, the backplate member comprises four or more opened windows for improving heat dissipation of the four or more sub-assemblies of the optical-electrical sub-modules. 